diff --git a/lucene/core/src/test/org/apache/lucene/util/fst/TestFSTs.java b/lucene/core/src/test/org/apache/lucene/util/fst/TestFSTs.java
index a6748a34865..e43107448d3 100644
--- a/lucene/core/src/test/org/apache/lucene/util/fst/TestFSTs.java
+++ b/lucene/core/src/test/org/apache/lucene/util/fst/TestFSTs.java
@@ -157,7 +157,7 @@ public class TestFSTs extends LuceneTestCase {
         final BytesRef NO_OUTPUT = outputs.getNoOutput();      
         final List<FSTTester.InputOutput<BytesRef>> pairs = new ArrayList<>(terms2.length);
         for(int idx=0;idx<terms2.length;idx++) {
-          final BytesRef output = random().nextInt(30) == 17 ? NO_OUTPUT : new BytesRef(Integer.toString(idx));
+          final BytesRef output = idx == 17 ? NO_OUTPUT : new BytesRef(Integer.toString(idx));
           pairs.add(new FSTTester.InputOutput<>(terms2[idx], output));
         }
         FSTTester<BytesRef> tester = new FSTTester<>(random(), dir, inputMode, pairs, outputs, false);